I've installed and used both. The inline rad hose install was more of a chalange working in a tight space. It was a Kats, and went into the 3T84 in my YM3000. Had to drain the coolant. Almost the same engine in my JD950 got a screw in block heater. ( 3T90J ) Hex head plug was behind the starter, had to remove the starter to unstick the plug, had to give it a little heat to break it loose. Think the 950 heats up faster with the block heater than the YM3000 did with the hose heater. Think a little more of the heat transfered to the radiator in the YM3000 than with the plug in the JD950. If I have it to do again with my new to me 970, I'll opt to do the screw in heater. I like unplugging the removable cord and getting it out of harms way in the summer.
Chris